In general, a covering resin layer of a waterproofing material, coated flooring material, sealing material, or the like is often provided in constructions formed with inorganic substrates such as mortar and concrete in order to prevent the inorganic substrates from corroding or deteriorating, and a primer is used as a surface-treating agent to improve the adhesiveness of the covering resin layer.
As typical examples of primers used in civil engineering and construction, those based on a urethane resin, epoxy resin, or the like can be mentioned. However, there has been concern about not only hazardous effects to the workers but also the indoor air pollution (a sick house) and the general air pollution. Therefore, it has been expected to reduce the use of the organic solvent therein by developing an aqueous primer, among others.
A primer used in the methods of waterproofing and floor-coating should be excellent not only in drying property directly after coating but also in basic properties such as permeability, shielding property, and adhesiveness to an inorganic substrate, and in durability such as water-proof adhesiveness. However, no aqueous primers having such properties have been developed although the organic solvent-based primers having these properties have been developed.
In general, aqueous resins can be classified into a water-soluble resin, and water-dispersible resin, which has a form of particles. The water-dispersible resin, in particular, the emulsion in which the particle diameter is large, is suitable in terms of the drying property at ordinary temperature, and the water-soluble resin is preferable in terms of its permeability to the inorganic substrates. That is, if the aqueous resin is used as a primer, it is difficult for the single water-soluble resin or the single water-dispersible resin to have all the required properties. Furthermore, tough hardening due to the cross-linking is required to impart durability such as water-proof adhesiveness.
In order to achieve these demands, a method in which an aqueous resin capable of cross-linking is used for surface-treating the inorganic substrate has been proposed. For example, a method in which an emulsifiable isocyanate prepolymer having hydrophilic groups is used for surface-treating by diluting with water (for example, see patent documents 1 and 2). This method is excellent in terms of not requiring an organic solvent, the impregnation into a porous inorganic substrate, and the reinforcement of the surface of the substrate. However, this method has a problem in which, if the isocyanate prepolymer is used for the method of water-proofing or floor coating, its drying is too slow to quickly go about the next step. Also, there is a problem in which covering resin layers of a water-proofing material, floor coating material or the like, which are coated thereon, are likely to be affected by the water content included in the bedding concrete and bulging is likely to be generated because they are inferior in shielding property.
A method in which an aqueous primer composition which includes an emulsifiable isocyanate prepolymer having hydrophilic groups and an emulsified resin solution is used for surface-treating, has been disclosed (for example, see patent document 3).
This method is excellent in terms of not requiring an organic solvent, the impregnation into a porous inorganic substrate, and the reinforcement of the surface of the substrate. However, this method has a problem in which, if it is used for the method of water-proofing or floor-coating, covering resin layers of a water-proofing material, floor-coating material, or the like, which are coated thereon, are likely to be affected by the water content included in the bedding concrete and bulging is likely to be generated because the molecular weight of the emulsified resin is small, so that they are inferior in shielding property. Also, this method has a problem in which its drying is too slow to quickly go about the next step in the case of the porous inorganic substrate which is not preheated with a hot air drying machine or the like.
An aqueous resin composition has been disclosed, which is made by combining three of an aqueous acrylate resin having hydroxyl groups and cross-linked structures, an aqueous urethane resin having hydroxyl groups and cross-linked structures, and a polyisocyanate compound dispersible in water (for example, see patent document 4). The coating materials made up of this composition are excellent in adhesiveness to resin substrates such as a urethane sheet, water-resistance, and water-resistant adhesiveness, but their permeability to inorganic substrates is low and their adhesiveness also tends to be inferior because their contents of the aqueous acrylate resin having hydroxyl groups are high.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. H6-92756
Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2004-010777
Patent Document 3: Japanese Unexamined Patent Application, Publication No. 2004-196914
Patent Document 4: Japanese Unexamined Patent Application, Publication No. 2000-265053